Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$136.46	4.288%	$142.3114	$142.31	$142.30	$142.30
Purchase #2	$18.29	6.248%	$19.4328	$19.43	$19.45	$19.40
Purchase #3	$146.51	12.275%	$164.4941	$164.49	$164.50	$164.50
Purchase #4	$224.88	3.824%	$233.4794	$233.48	$233.50	$233.50
Purchase #5	$71.37	3.762%	$74.0549	$74.05	$74.05	$74.10
Purchase #6	$130.99	13.662%	$148.8859	$148.89	$148.90	$148.90
Purchase #7	$227.64	12.755%	$256.6755	$256.68	$256.70	$256.70
7 purchase totals =	$956.14		$1,039.3340	$1,039.33	$1,039.40	$1,039.40